Browsing by Author "Matsuki, Noriaki"
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- Blood flow in microchannel with stenosis measured by a confocal micro PTV systemPublication . Fujiwara, Hiroki; Ishikawa, Takuji; Lima, Rui A.; Imai, Yohsuke; Matsuki, Noriaki; Kaji, Hirokazu; Mori, Daisuke; Nishizawa, Matsuhiko; Yamaguchi, TakamiBlood in microcircualtion is not a homogenous fluid but the suspension of Red Blood Cells(RBC). So individual RBCs behavior is essential to get good comprehension about the blood flow in microcirculation. In this study we observe the RBCs behavior through the stenosis by using confocal-micro- PTV system. And we can observe the difference of the cell free layer thickness according to Hct.
- Blood-on-chips: flow through complex geometriesPublication . Lima, Rui A.; Oliveira, Mónica; Ishikawa, Takuji; Matsuki, Noriaki; Imai, Yohsuke; Yamaguchi, TakamiBlood is a complex body fluid, composed of cells and plasma, which holds a massive amount of information about several physiological and pathologic events happening throughout the body. Hence, blood sampling and analysis are used extensively in traditional clinical laboratories for the diagnosis of several diseases. Since the inception of microfluidics, there has been a growing interest, by both microfluidic and biomedical communities, to develop blood-on-chip devices as an alternative tool for the diagnosis of major diseases, such as cancer and cardiovascular diseases. Therefore, it is essential to understand the blood flow behaviour involved in this kind of microfluidic channels in order to design reliable blood-on-a-chip devices able to efficiently treat and diagnose a variety of diseases. The present experimental study shows the effect of micro-scale contractions and expansions, such as those found in an artificial stenosis, on the blood flow and cell behaviour. The micro-channels were fabricated in PDMS using softlithography and the experiments were carried out by using dextran 40 containing different fractions of human erythrocytes. The in vitro blood flow was measured by means of a high-speed video microscopy system composed with an inverted microscope, a high-speed camera and a thermo plate to control the surrounding temperature.
- Dispersion of red blood cells in microchannels : a confocal micro-PTV assessmentPublication . Lima, Rui A.; Ishikawa, Takuji; Imai, Yohsuke; Fujiwara, Hiroki; Takeda, Motohiro; Matsuki, Noriaki; Wada, Shigeo; Yamaguchi, TakamiBlood in large arteries may be treated as a homogenous fluid from a macroscopic prospective. However, in reality blood is a suspension of deformable cells in viscous fluid plasma. In microcirculation, which comprises the smallest arteries and veins, the flow behavior of individual blood cells and their interactions provide the microrheological basis of flow properties of blood at a macroscopic level. Hence, in microcirculation it is fundamental to study the flow behavior of blood at cellular level. Several studies on both individual and concentrated RBCs have already been performed in the past. However, all studies used conventional microscopes and also ghost cells to obtain visible trace RBCs through the microchannel. The present study is concerned in providing further insights into the microscale blood flow behavior through microchannels by applying an emerging optical technique known as confocal micro-PIV/PTV. The technique consists of a spinning disk confocal microscope, high speed camera and a diode-pumped solid state (DPSS) laser combined with a single particle tracking (SPT) software (MtrackJ). Detailed measurements on the motions of RBCs were measured at different haematocrits (Hct) and the correspondent radial dispersion coefficient was determined.
- Individual motions of red blood cells in high-hematocrit blood flowing in a microchannel with complex geometriesPublication . Ishikawa, Takuji; Fujiwara, Hiroki; Matsuki, Noriaki; Lima, Rui A.; Imai, Yohsuke; Ueno, H.; Yamaguchi, TakamiBlood flow in a microchannel with complex geometries has been investigated to develop biomedical microdevices (e.g. Faivre et al., 2006) or to understand pathology in small vessels, such as lacunar infarcts. In a small channel, say 100 μm in diameter, the blood is no longer assumed to be a homogeneous fluid because the size of the red blood cells (RBCs) cannot be neglected compared to the generated flow field (the diameter of a RBC is about 8 μm). In such a case, we must treat the blood as a multiphase fluid, and investigate the motion of individual cells in discussing the flow field. In this study, we investigated the motion of RBCs in a microchannel with stenosis or bifurcation using a confocal micro-PTV system. We measured individual trajectories of RBCs under high Hct conditions (up to 20%), when the interactions between RBCs become significant. We discuss the effect of Hct on the flow field and cell-free layers, as well as the effect of deformability of RBCs on the cell-free layer thickness by hardening RBCs using a glutaraldehyde treatment.
- Measurement of multi-red blood cells interactions in blood flow by confocal micro-PTVPublication . Lima, Rui A.; Ishikawa, Takuji; Fujiwara, Hiroki; Takeda, Motohiro; Imai, Yohsuke; Tsubota, Ken-ichi; Matsuki, Noriaki; Wada, Shigeo; Yamaguchi, TakamiIn microcirculation the flow behavior of red blood cells (RBCs) plays a crucial role in many physiological and pathological phenomena. For instance, the interaction of RBCs in shear flow is believed to play an important role to the thrombogenesis process. Despite the relevance of this phenomenon on the blood mass transport, very little studies have been performed during the years, partly due to the absence of adequate visualization techniques able to obtain both direct and quantitative measurements on multi-RBCs motions in concentrated suspensions. Past studies on both individual and concentrated RBCs used conventional microscopes and/or ghost cells to obtain visible trace RBCs at high concentration suspension of blood cells [1, 2]. Recently, advances of confocal microscopy and consequent advantages over conventional microscopes have led to an emerging technique known as confocal micro-PIV [3, 4]. This paper presents the application of a confocal micro- PTV system to measure RBC-RBC hydrodynamic interactions in flowing blood.
- Mixing of red blood cells in a micro-channel flow under high hematocrit conditionsPublication . Ishikawa, Takuji; Lima, Rui A.; Fujiwara, Hiroki; Imai, Yohsuke; Matsuki, Noriaki; Yamaguchi, Takami
- Motion of individual red blood cells in a concentrated suspension flowing through micro-channelsPublication . Ishikawa, Takuji; Fujiwara, Hiroki; Matsuki, Noriaki; Lima, Rui A.; Imai, Yohsuke; Yamaguchi, TakamiIn this study, we use a confocal micro-PIV (Particle Image Velocimetry) system to investigate red blood cell motions flowing in micro-channels. This system enables us to visualize the individual RBCs even in the high Hct blood by exciting the labeled RBCs by the laser. We measure individual trajectories of RBCs in a micro-channel with stenosis or bifurcation under high Hct conditions. Our results clearly demonstrate that the trajectories of RBCs strongly depend on the hematocrit, the RBC property and the position in the micro-channel. This information is important for a better understanding of mass transport in the microcirculation.
- Motion of red blood cells and cell free layer distribution in a stenosed microchannelPublication . Fujiwara, Hiroki; Ishikawa, Takuji; Lima, Rui A.; Imai, Yohsuke; Matsuki, Noriaki; Mori, Daisuke; Yamaguchi, Takami
- Observation of blood flow in microchannel with stenosis by confocal micro-PIVPublication . Fujiwara, Hiroki; Ishikawa, Takuji; Lima, Rui A.; Kaji, Hirokazu; Matsuki, Noriaki; Imai, Yohsuke; Nishizawa, Matsuhiko; Yamaguchi, Takami
- Red blood cell motions in high-hematocrit blood flowing through a stenosed microchannelPublication . Fujiwara, Hiroki; Ishikawa, Takuji; Lima, Rui A.; Matsuki, Noriaki; Imai, Yohsuke; Kaji, Hirokazu; Nishizawa, Matsuhiko; Yamaguchi, TakamiWe investigated the behaviour of red blood cells (RBCs) in a micro-channel with stenosis by using a confocal micro-PIV system. We could successfully measure individual trajectories of RBCs in a concentrated suspension up to 20% hematocrit (Hct). The results show that the trajectories of healthy RBCs become asymmetric before and after the stenosis, though trajectories of tracer particles in pure water are almost symmetric. The asymmetry is larger in a 10% Hct case than in a 20% Hct case. We also investigated the effect of deformability of RBCs on the trajectories by hardening RBCs by glutarardehyde treatment. The results indicate that the deformability is the key factor in the asymmetry of trajectories and the thickness of cell-free layer. We think that the present results give fundamental knowledge for better understanding blood flow in microcirculations.